Find $\lim_{x\to -2}\dfrac{x^3+3x^2+2x}{x+2}$. Choose 1 answer: Choose 1 answer: (Choice A) A $6$ (Choice B) B $0$ (Choice C) C $2$ (Choice D) D The limit doesn't exist
Explanation: Substituting $x=-2$ into $\dfrac{x^3+3x^2+2x}{x+2}$ results in the indeterminate form $\dfrac{0}{0}$. This doesn't necessarily mean the limit doesn't exist, but it does mean we have to work a little before we find it. Since we have a rational expression on our hands, let's try to simplify it. $\dfrac{x^3+3x^2+2x}{x+2}$ can be simplified as $x^2+x$, for $x\neq -2$. This means that the two expressions have the same value for all $x$ -values (in their domains) except for $-2$. We can now use the following theorem: If $f(x)=g(x)$ for all $x$ -values in a given interval except for $x=c$, then $\lim_{x\to c}f(x)=\lim_{x\to c}g(x)$. In our case, $\dfrac{x^3+3x^2+2x}{x+2}=x^2+x$ for all $x$ -values in the interval $(-3,-1)$ except for $x=-2$. Therefore, $\lim_{x\to -2}\dfrac{x^3+3x^2+2x}{x+2}=\lim_{x\to -2}(x^2+x)=2$. (The last limit was found using direct substitution.) [I want to see how this looks graphically!] In conclusion, $\lim_{x\to -2}\dfrac{x^3+3x^2+2x}{x+2}=2$.